The tooth count of the blade you should use has more to do with the thickness of the metal you are cutting and not the hardness. A high tooth count will cut anything, but will be slow in thicker metals. Low tooth counts will work well in thick metals, but they break teeth off when you try to cut the thin stuff. Depending on the hardness of the metal, you will need to select a blade material to match. Cobalt and Bimetal blades work best for harder metals like stainless.